We are evaluating and describing the craniofacial and dental anomalies in mice with X-linked dominant hypophosphatemia (vitamin D-resistant rickets). The symptoms of the disease in these mice closely mimic those seen in humans with VDRR. We are using the following techniques in our study: 1) cephalometry, 2) craniometry, 3) histology and 4) histochemistry. By utilizing the appropriate genetic crosses, we are studying mice of the three possible genotypes (hemizygous males, heterozygous females and homozygous females). We will assess the craniofacial differences in prenatal and neonatal as well as in young, adult and senile animals. We hope to be able to time the appearance of the various craniofacial anomalies and to assess the effectiveness of present and experimental therapeutic approaches used to treat the disease in humans.